As the cancer therapeutic method, a chemotherapy in which various antitumor agents are administrated, an immunotherapy in which production of an antibody to cancer cells is accelerated, a surgical therapy in which cancer cells are removed or enucleated, radiotherapy in which cancer cells are killed by irradiating radioactive rays upon them, etc. are employed.
However, even if a primary cancer is completely healed, a problem may still exist. That is, the reason why the cancer is a malignant tumor is that the cancer is metastatic, and that persons are often killed with metastatic cancers provoked by metastasis of cancer cells. It cannot be said that a method for suppressing the metastasis of the cancer cells has been established, and it is a present situation that a medicine having a cancer cell metastasis suppressing effect has not yet been made commercially available.
On the other hand, a few or several steps are considered for the metastasis mechanism, and a casual relationship between the cancer metastasis and the sugar chain has been recently discussed in academic meetings. In the metastasis of the cancer cells, cancer cells are first released from a cancer-developed site, and are carried and moved through a human body with blood. E-selectin as one of intercellular adhesive molecules appears on the surface of an intravascular endothelial cell for a certain reason. This E-selectin interacts with free cancer cells moving through the human body with blood, which causes a rolling phenomenon in which the free cancer cells roll on the surfaces of the intravascular endothelial cells and reduce their moving speed in the blood. Consequently, the free cancer cells are adhered to the intravascular endothelial cells through the rolling phenomenon. Then, the cancer cells pass between the intravascular endothelial cells, and enter vascular tissues, so that a new cancer cell nest is formed (See FIG. 1).
In this series of steps, the adhesion between the E-selectin, appearing as one of the intercellular adhesive molecules, on the surface of an intravascular endothelial cell and the sugar chain present at the surfaces of the cancer cells plays a very important role in an initial stage of the adhesion between the cancer cells and the intravascular endothelial cells. As an antibody against the sugar chain at the surface of the cancer cell which sugar chain interacts with the E-selectin, sialic acid-containing complex sugar chains called sialyl Le.sup.a and sialyl Le.sup.x have been identified.